In order to protect coral reefs it is important to understand how both the reefs and their environment function. Researchers often concentrate on subjects such as physical damage to reefs, the bleaching of coral and coral diseases. Sander Scheffers investigated a lesser-studied subject: the nutrient cycle on the coral reef and the role that organisms living in cavities, such as sponges, play in this.
To determine the nature and size of this role, Scheffers first of all examined the precise appearance and quantity of these virtually inaccessible caves and their living communities. He did that on the Caribbean island of Curaao using a special underwater camera. The films shot revealed that sponges were the most important inhabitants, followed by animals such as tube worms, tunicates and bivalves. Together they fill more than 60 percent of the cavities. Further the cavities were found to have a surface area eight times greater than that of the coral reef, as seen from above by divers.
And according to Scheffers a larger living surface also means a larger filtering surface. Sponges filter the water. They take up planktonic particles such as bacteria and excrete inorganic nutrients. In turn, these nutrients can facilitate the growth of marine plants and other organisms.
Sponges filter at a phenomenal rate: if the seawater were to remain stationary, the sponges would have completely pumped it away within five minutes, i.e. they would have removed all of the small plankton from it. This is of course not the case, as there is a continuous supply of fresh water into the sea
Source:Netherlands Organization for Scientific Research